Question

Calculate the square value of $28$ using direct multiplication method.

Answer 1

We can write ${28}^2=(20+8{)}^2$

Using $(a+b{)}^2=a(a+b)+b(a+b)$
Here $a=20,b=8$
Therefore, ${28}^2=20(20+8)+8(20+8)$
$=$ ${20}^2+160+160+8^2$
$=400+320+64$
$=784$